The widespread implementation of communication devices has increased network traffic and the need for higher bandwidth. In known communication systems, for managing large, continuous and error-free data traffic, the networks use different network topologies. These network topologies generally include multiple interconnected nodes. Attempts are being made to improve the existing networks by developing communication systems that can support more complex network topologies and greater network bandwidths.
Fiber-optic communication is typically used presently due to its large data bandwidth and fast data transfer. One commonly implemented method to increase data bandwidth is through Dense Wavelength Division Multiplexing (DWDM), which is used to multiplex data from different optical sources together on each optical fiber, with each optical signal having its own separate light wavelength. Known optical communication systems based on the DWDM technology typically include one or more reconfigurable optical add/drop multiplexer nodes (ROADM nodes) each of which typically has multiple ROADM cards. A typical ROADM card includes a Wavelength Selective Switch (WSS) that performs both wavelength selection and channel power equalization.
Other optical transmission systems use coherent technology for high data rate signals (e.g., 100 Gb/s & higher). Such coherent optical transmission systems are much less tolerant to optical signal to noise ratio (OSNR), and to impairments such as polarization dependent loss (PDL) when compared to non-coherent optical transmission systems. Coherent optical communication systems are expected to have very high port count (˜40 or more) ROADMs. But, the known ROADMs typically do not scale well beyond about 20 ports because as the number of ports increases, at some point the optical performance of the wavelength selective switches (WSSs) of the ROADMs degrades precipitously.
Thus, a need exists for ROADMs with higher port counts with improved signal-to-noise ratios and lower optical system penalties.